The alleged mastermind behind the Al-Shabaab terror attack in Kenya's Garissa Univeristy on Thursday is a Kenyan himself, who used to teach at a madrassa before joining the Somalian outfit.

Mohamed Mohamud, also known as Sheik Dulayadayn, now has a £145,000 ($215,000) bounty on his head for planning the deadliest attack in Kenya since the American embassy bombing in 1998.

The Garissa univeristy attack was apparently Mohamud's way of avenging his colleagues' deaths at the hands of Kenyan forces, according to The Star newspaper.

An engineering graduate from Jomo Kenyatta University in Nairobi, Mohamud had moved towards Islamic teachings, working at the Al-Haramain Foundation and then as a principal of a madrassa in Garissa till 2007.

Hailing from the Ogaden tribe, he has been married to three women, two from Garissa and the third from Somalia.

After becoming increasingly radicalised, Mohamud crossed over into Somalia to join the Islamic Courts Union, a movement that had brought Sharia courts to form a parallel government in the country.

After the movement ended, Mohamud joined the Hizbul Islam militant outfit and then found himself part of al-Shabaab after the two terror groups joined in 2010. Two of his brothers are also part of the terror group,The Star newspaper reported.

Even before the Garissa attack, Mohamud had a bounty on his head due to his role in the Westgate shopping mall attack in Nairobi and the Mandera bus killings of non-Muslims, for which he had claimed responsibility.